(Android review) basic use of handler

(Android review) basic use of handler

I. Basic knowledge points

1. Intent intent = new Intent (); // open the browser's
Intent. setAction (Intent. ACTION_VIEW );
Intent. setData (Uri. parse ("http://www.baidu.com "));


2. SystemClock. sleep (20000); // sleep for 20 seconds to hide the game


3. Time-consuming operations should be performed in sub-threads
Obtain data online
Copying large files
Must be placed in the sub-thread for operation.


The onCreate () button clicks the callback event and the displayed operations are all run in the main thread. UI thread.


4. handler usage
New Handler ();


Message msg = new Message ();
Msg. what = UPDATE_DISPLAY; // sets unique message recognition.
Msg. obj = I;
MHandler. sendMessage (msg)

Ii. Sample Code

package com.example.handlertest;import android.os.Bundle;import android.os.Handler;import android.os.Message;import android.os.SystemClock;import android.app.Activity;import android.view.Menu;import android.view.View;import android.widget.TextView;public class MainActivity extends Activity {public TextView tv_num;public static final int UPDATE_NUMBER = 0;public int i = 0;public Handler handler = new Handler(){public void handleMessage(android.os.Message msg) {if(msg.what == UPDATE_NUMBER){int i = (Integer) msg.obj;tv_num.setText(i + "");}};};@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);tv_num = (TextView) findViewById(R.id.tv_number);}public void add(View view){new Thread(){@Overridepublic void run() {super.run();while(i < 100){SystemClock.sleep(1000);i += 1;Message msg = new Message();msg.what = UPDATE_NUMBER;msg.obj = i;handler.sendMessage(msg);}}}.start();}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);return true;}}

3. Download source code

Http://download.csdn.net/detail/caihongshijie6/7798627

IV,